How much advance!
Discussion
Hi Guys...
The vehicle is a "standard" TVR 350i, running ordinary unleaded fuel, with thicker, composite, head gaskets which reduce the compression ratio slightly.
After setting the ignition timing (800 rpm, vacum disconnected and plugged) to 8 degrees, I increased the engine rpm to observe how much mechanical advance I was seeing. Observed 10-12 degrees of additional advance, making 20-22 degrees in total. When I re connected the vacum there didn't appear to be any more advance over the 20-22 observed earlier.
My question is, how much advance should I expect the vacum to contribute? Previously when the car has been on rollers the operators have mentioned "maximum advance" of something like 27 degrees... (at 22 degrees I'm well short of this) Should I be able to see this sort of figure with a strobe light without the engine running some sort of load?
Can someone can explain what the "maximum advance" figure is and how it is measured, because the manuals I'm reading don't seem to mention it at all.
My other concern(?) is that even with the timing set at 10 degrees, I am unable to make the engine pink, making me further suspect that the vacum unit on the distributor needs replacing. This isn't normally the problem with this engine on unleaded fuel!
Any part numbers for the vacum unit would be appreciated.
Just to be clear, all measurements are degrees BEFORE TDC.
Regards,
Brian (and a Red 350i)
The vehicle is a "standard" TVR 350i, running ordinary unleaded fuel, with thicker, composite, head gaskets which reduce the compression ratio slightly.
After setting the ignition timing (800 rpm, vacum disconnected and plugged) to 8 degrees, I increased the engine rpm to observe how much mechanical advance I was seeing. Observed 10-12 degrees of additional advance, making 20-22 degrees in total. When I re connected the vacum there didn't appear to be any more advance over the 20-22 observed earlier.
My question is, how much advance should I expect the vacum to contribute? Previously when the car has been on rollers the operators have mentioned "maximum advance" of something like 27 degrees... (at 22 degrees I'm well short of this) Should I be able to see this sort of figure with a strobe light without the engine running some sort of load?
Can someone can explain what the "maximum advance" figure is and how it is measured, because the manuals I'm reading don't seem to mention it at all.
My other concern(?) is that even with the timing set at 10 degrees, I am unable to make the engine pink, making me further suspect that the vacum unit on the distributor needs replacing. This isn't normally the problem with this engine on unleaded fuel!
Any part numbers for the vacum unit would be appreciated.
Just to be clear, all measurements are degrees BEFORE TDC.
Regards,
Brian (and a Red 350i)
sounds to me that the mech inside your dizzy needs looking at, the vacuum advance unit won't add any spark on full throttle and you should be getting about 30-32° above 3500Rpm. I think the vacuum unit tends to add 5-6° part throttle and above idle, as the std tapping on the rover is partly covered by the butterfly at idle.
Matt
Matt
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff